Re: rescan scsi

Gerald Britton (
Fri, 20 Jun 1997 13:13:00 -0400 (EDT)

On Fri, 20 Jun 1997, ;The Doctor What wrote:

> I have a question....why do people say NOT to add scsi devices on the
> fly to a system? I thought that was (inpart) the point of SCSI?
> The only things I can think of is:
> 1) The device generates a "startup" message that does evil things to
> the SCSI card. (Which doesn't make sense, since I always turn off
> external scsi devices if I'm not using them for an extended period of time).
> 2) There is a chance of an electrical discharge that frys hardware....

#2 is the reason why people say not to hotadd stuff... this in general
goes for any componant.. including parallel ports etc.. i've never run
into a problem with this before. There are HotSwap scsi busses which have
trays with connectos to provide safe insertion into a running system..
i've hot inserted devices into this type of system with no problem. I
have also inserted devices into non-hotswap systems without problem. one
thing you might run into hot swapping scsi is termination.. you'll need to
remove the terminator to add a new device.. do this quickly, as the scsi
device will likely give errors during this period.. it _usually_ won't be
a problem, but it might be.

> 3) You might accidentally be sucked into the computer and be forced to
> play silly 80's games involving frisbees and glowing cycles.
> Of course, I work for Tandem and we ALWAYS hot-swap stuff (except for
> $SYSTEM, aka the /root partition ;), and only a few operators have
> become victims of the MCP.
> (Holy Tron references, Batman!)
> --
> The Doctor What: Guru of the Gods
> (finger for PGP key)
> PGPkey Fingerprint: EA 4C 8C FC 5C F0 14 78 9C 02 B9 A1 83 54 7C 8D

Gerald Britton